1. Field of the Invention
The invention relates to a method and an apparatus for checking documents of value, in particular for checking the usage state of documents of value.
2. Related Art
With the passing of time that documents of value, such as e.g. bank notes, are in circulation or in use, the usage state thereof deteriorates. The usage state may diminish to the unserviceability of the documents of value. In order to recognize a poor usage state in time, documents of value are therefore regularly checked by machine for their usage state and if their usage state is judged to be too poor are automatically sorted out. The check of the usage state is usually carried out e.g. in cash deposit and/or dispensing machines for bank notes or also in bank note sorting machines, whereby the authenticity and the denomination of the bank notes is also checked.
For checking the usage state of a document of value, in particular the fitness of the document of value, the document of value is usually examined for the presence of tears or dog-ears. Additionally, there can also be checked the soiling of the document of value, whereby e.g. certain areas of the document of value are checked for the presence of stains. In certain areas of the document of value the checking for stains is difficult, e.g. when the stains are superimposed on a dark or a patterned, colored background of the document of value. Moreover, it is known to check documents of value for their limpness, e.g. with the help of ultrasonic measurements.
Starting out from the stated prior art, the invention is based on the object of providing a further method which can be used for checking the usage state of documents of value.